An electro-hydraulic variable valve train with a generic subassembly is apparent from EP 1,344,900 A2. An important element of this valve train—which operates, as is generally known, according to the so-called lost motion principle—in which a so-called hydraulic linkage with variable, controllable hydraulic volume runs between the input end, which is to say the cam of a camshaft, and the output end, which is to say the gas exchange valve, is a hydraulic valve brake that controls the contact speed of the closing gas exchange valve independently of the cam position and limits it to predefined values that are acoustically and mechanically acceptable.
The hydraulic valve brake is a valve element implemented as a throttle check valve. The controlled braking of the piston and consequently of the gas exchange valve, which is spring-loaded in the closing direction, is accomplished by means of the throttle opening, which produces a strong throttling of the hydraulic medium displaced from the pressure chamber in the final closing phase of the gas exchange valve. By contrast, the purpose of the ball check valve that is closed during the valve closing phase is to permit a fast initial opening speed of the gas exchange valve in that an essentially unthrottled, and accordingly comparatively large, volume flow can enter the pressure chamber when the valve ball is then opened.
The valve element is located in a fixed position in a hydraulic housing that is placed in the cylinder head of the internal combustion engine and includes the primary elements of the hydraulic valve train. The valve element is fastened in the hydraulic housing by means of a screw that braces a guide bushing against the valve element and braces the valve element against the hydraulic housing.